at this point, we primarily have sulfate particles. using cutting-edge instruments aerodyne research can detect tiny concentrations of pollutants in real time acking them back to their sources and showing how they evolve hour by hour under the effects of sunlight and weather. in mexico city luisa molina is leading a group of over 450 scientists in the most comprehensive study ever conducted of one city's air emissions. sampling its plume of pollutants from cradle to grave the team hopes to learn how the city's pollution affects the surrounding regions and even the global climate. today, the rapid increase of population and industrialization is causing increasing concerns about air pollution. both researchers hope to discover what's causing the most damage and find ways to reduce the human and global impact.
[ horn honks ] kolb: one of the real facts that we all have to deal with is that people make pollution, and as the population of the earth grows unless we're very clever and work very hard the levels of pollution we all have to live with will grow along with it. we have to understand which pollutants are the ones that we must control, and we have to come up with either changes in our technology or changes in our lifestyles which reduce the heavy pollution burdens that we emit into the atmosphere. narrator: charles kolb is president of aerodyne research a company that specializes in studyinair pollution and designing instruments to hp measure it.
a new aerosol mass spec body. kolb: our air-pollution research focuses on what's emitted by various pollution sources -- cars, trucks, planes, factories, and many other sources -- and to understand how they change the atmosphere and how that changed atmosphere turns around and impacts people and the climate and the ecosystems that we want to preserve. narrator: air pollutants exist as harmful gases or as aerosols. aerosols are microscopic solid or liquid particles suspended in the air and these pollutants can have deadly effects. kolb: most of us can only survive a minute or so without a fresh breath of air, and if the air contains substances which are going to really hurt your health, you'd hate to think that you're shortening your life with every breath of air you take.
narrator: the worst air-pollution disaster on record occurred in london in december of 1952. at this time, londoners still consumed lots of coal, which led to large amounts of pollutants in the air including black carbon or soot particles, and sulfur dioxide. and this toxic mix turned fatal. kolb : the particle loading got so heavy during one episode that the so-called killer fogs actually killed many thousands of people over about a week and a half. narrator: thanks to regulations to reduce these pollutants events like this are rare today. however, public health officials estimate that 70,000 americans die prematurely each year due to air pollution.
in order to monitor these pollutants kolb and his team at aerodyne research devoped a series of revolutionary laboratory-grade instruments that could be deployed from a mobile van. kolb: we've developed some very capable and very fast research instruments that can be deployed in the atmosphere and measure right away what's there. narrator: traditionally, samples had to be brought back to the lab to be analyzed, but with the mobile van, measurements are instantaneous. the benefit of using real-time instrumentation is that it maximizes the scientific impact that we're able to have when we're out in the field. it looks like we're picking up a good sulfate plume. kolb: the mobile lab is equipped with instruments that can measure every second or so. if you're characterizing an emissions source, and its emissions are changing second
by second as a vehicle might as it stops and starts or accelerates or goes up a hill, then if you don't measure second by second you won't get the right answer. nitrates? yeah, i see some nitrates. narrator: one key instrument is aerodyne's aerosol mass spectrometer, which measures thtiny suspended particles in the atmosphere. what's really special about it is that usually when you're looking at particles you just know sort of how many particles are in your sample. but what the ams is capable of doing is telling you what the chemical species of each of those particles is. you can say, "oh, you know there's 1,000 particles in this cubic centimeter of air," roughly this big but you can also say "oh, a certain fraction of them are sulfate, "a certain fraction of them are some sort of organic a certain fraction of them are nitrate," et cetera, et cetera. and so that gives you a much stronger capability because it turns out that the way these particles interact with the environment, for instance how they might or might not affect
global warming, depends upon their composition. and how they might affect or might not affect human health depends on their composition as well as their size. herndon: if you're concerned about the health impacts you're most concerned about the size of particles that are sufficiently small so that they go into your lungs, deep into your lungs along with the gas flow. and in that case you could actually be introducing some things into your body into your bloodstream, quickly that have no business being there. narrator: particles less than 10 micrometers in diameter, just a fraction of the width of a human hair, can lodge deep into the lungs. those smaller than 2.5 micrometers classified as "fine particles," have been linked to the most serious health problems. kolb: it can lead to a number of medical complications including not just lung disease --
emphysema, asthma, possibly lung cancer -- but can also put a very high strain on your heart and can lead to heart attacks. narrator: aerodyne measures both the hazardous particles and the pollutant gases being emitted from various sources. you'd think you'd see some sulfate, but i don't know. kolb: we want to use our mobile laboratory to understand pollutants that are directly emitted into the atmosphere. we call those "primary pollutants." with a mobile laboratory you can actually map out the distribution of the air pollutants so that you have a much better picture of how the pollutants are dispersed around, say, a city, or around a factory complex. in addition, you can locate sources of pollutants because you can see a concentration in a plume and you can then use the mobile laboratory to actually follow the plume back to the source.
narrator: vehicle emissions are one of the sources of primary pollutants tracked by aerodyne. while the emissions from an individual car are relatively low compared with factories, in many cities, the millions of vehicles on the road add up to be the most serious threat to clean air. vehicle exhaust pollutants include aerosols and these gases... using their trace-gas detector the aerodyne team can monitor these pollutant gases, even at very low levels. but these pollutants by themselves, are not the only concern. some primary pollutants, such as nox, become even more dangerous when they begin a complex chemical reaction after being exposed to sunlight.
second big job with the mobile lab is to go out and actually then see what happens to those primary pollutants as they cook in the atmosphere. this chemistry can create what we call "secondary pollutants." it can chemically change the pollutants that were emitted into the atmosphere into different and sometimes more dangerous chemicals. narrator: one secondary pollutant that concerns scientists is ozone. ozone is a gas made up of 3 oxygen molecules, and it can have both good and bad effects, depending on where it's located. the stratospheric ozone layer protects the earth from harmful ultraviolet rays, but ground-level ozone in the troposphere is highly reactive and can cause irritation of the respiratory system, permanently scarring lung tissue. kolb: ozone is a very powerful oxidant.
it can kind of bleach the cells in your body and can create a lot of serious problems, both to people to other animals, and to plants. narrator: the main precursors in creating ozone are nitrogen oxides, emitted from vehicles and other combustion sources and hydrocarbons the result of combustion other industrial processes and vegetation. when these pollutants interact in the presence of sunlight, they produce ground-level ozone. sunlight causes nitrogen dioxide, no2, to separate into nitric oxide, "no," and an oxygen atom. the oxygen atom adds to naturally occurring molecular oxygen, or o2, to create ozone. but this is just the first step in a chain reaction of ozone production. the remaining nitric oxide reacts with unstable molecules
that are products of hydrocarbons oxidizing in the atmosphere, recreating nitrogen dioxide, causing a vicious cycle of ozone production. kolb : so ozone gets formed as a secondary pollutant. it's not emitted directly, and it's important to understand not only how much ozone is in the atmosphere but how much of its precursor chemicals are there so we can predict what the ozone will look like as the wind blows that chemical mixture across the countryside. narrator: aerodyne's van has been deployed all over north america to help engineers and planners identify the best strategies to reduce pollutants from industries and transportation systems. kolb: we've worked with the metropolitan transit authority in new york city that runs about a third of the city's buses, to determine which types of buses
emit what kinds of pollutants. so one can take the mobile lab and follow the buses as they go about their routes in the city. and as they stop and start take on passengers accelerate, slow down, one can see how both the particle pollutants and the gaseous pollutants they emit change. then you can take the same type of bus and put some emission-control technology on it -- maybe a trap that traps and burns the particles -- and you can see what effect that has on the particle emissions and also what effect it has on the gaseous emissions. narrator: when kolb's team tested these buses they found some unexpected results. kolb: the diesel buses with particle traps did, indeed, emit only about a quarter of the particles that normal diesel buses emitted, but they did emit a large amount of nitrogen dioxide, which is, again, a gas that is a toxic air pollutant.
so you have to be careful, when you're trying to solve one pollution problem, that you don't create a second pollution problem which may be as serious as the first one. narrator: in europe and the united states, policies have been put in place to reduce air pollution. the clean air act of 1970, which set limits on concentrations of certain pollutants, along with subsequent programs hasignificantly improved air quality. kolb: since 1970 we've had fairly strict laws which have helped stop the increase in bad air-pollution episodes and, in fact, in most cities have decreased them. but in cities with rapid growth and with challenging climates -- climates that can lead to a lot of chemistry in the air and a lot of secondary pollution formation, there are certainly still big challenges
left. narrator: developing innovative ways to measure primary and secondary pollutants is a necessary first step in creating effective strategies for protecting human health. but measuring the local air pollution from cars and factories is just one piece of the puzzle. atmospheric circulation carries pollutant streams far beyond the metropolitan areas where they are created causing regional and even global effects. and so the pollutions that are created in the large megacities in china can deliver very high levels of pollutants all across the united states just as the pollution that's created in the midwest and the eastern part of the united states reaches all the way to europe. it only takes about two weeks for air to go all the way around the world. narrator: and some pollutants,
such as aerosols and greenhouse gases like carbon dioxide and ozone, even affect the global climate. so we don't have the luxury of thinking that it's other people's air-pollution problems other people's climate problems. if they're having problems we're going to have problems, too. narrator: and one of the biggest emerging threats to the global environment is increased air pollution from megacities. a megacity is defined having 10 million or more inhabitants. currently, there are over 20 megacities worldwide and that number continues to grow at an alarming rate. hundreds of millions of people currently live in these cities and it is projected that by the middle of the century this number will be multiplied many times over, with 60% of the world's population living in urban areas.
this rapid growth means an ever-rising toll to human health unless we gain a better understanding of the life cycle of air pollutants. and that's exactly what's being done in mexico city for the milagro project, the largest coordinated study ever conducted of megacity air pollution. 1, 2, 3. luisa molina is the project coordinator and one of the lead scientists on this effort. molina: "milagro" stands for "megacity initiative local and global research observations." and we were very, very pleased that we were able to find an acronym, milagro, that not only fit the themes of our measurement campaign, but it also means "miracle" in spanish. narrator: in march 2006, molina gathered an international team of more than 450 scientists
to investigate the effects of local pollution in mexico city on the surrounding regions and the global atmosphere. the scientists represent over 50 academic and research institutions from mexico, europe, and the united states, including nasa the department of energy and the national science foundation. mexico city is an ideal location for milagro's megacity resrch. surrounded on three sides by mountains pollutants become trapped within the city. molina: there are many reasons for selecting mexico city. first of all, mexico city is one of the largest megacities. it has about 20 million people. it is in a tropical latitude so it's representative of many of the future megacities which will be in asia, in africa.
mexico city is at a high altitude and the solar radiation is very strong and the photochemistry it is very reactive. and of course, what we hope is that what we learn from mexico city it will provide insight for us so that we can use that insight and understanding and apply it to other future megacities. narrator: while many previous studies revealed a great deal about pollution within mexico city what happened to the pollution after it left the city and what its effects were on the region and the globe had never been systematically studied until milagro. so you have all this pollution coming out from burning of fossil fuels from cars, from industry. and so the pollutants that emitted locally the local effects would be on the health of the population and on the air quality. but then they could also -- the regional impact, which would affect the ecosystem.
and then, also there's the global impact that would affect the climate. so this is very serious. narrator: 24 hours a day for 30 days the milagro team collected data using airplanes, radars, weather balloons and dozens of scientific instruments. i brought here to mexico city an instrument which i call the differential supersaturation separator. our instrument is called a long-path differential optical absorption spectrometer. photoelectric aerosol sensor. a proton transfer mass spectrometer. this is what we call a caps probe, which stands for "cloud aerosol and precipitation spectra" probe. what it measures is aerosol particles which are the very fine particles in the air. as we fly, it's in front of the plane because there would be engine exhaust if it was further back so it sees the air first. aerosol air comes through this probe
and what is detected is the size of the particles. by simultaneously and collaboratively gathering their data the scientists will have better information to create new models for predicting the transport of pollution over wide geographic areas. molina: the objective of this study, of milagro, is to follow the plumes and find out where and how and when the plumes are transported to other regions. and so it is very important for us not only just to look at one site, but to look at various sites. narrator: to study the movement of plumes, the researchers have three main fixed ground sites -- "t0," located in the center of the city, and t1 and t2, two points north of the city where the prevailing winds are expected to carry the plumes. at these sites, research teams measure trace gases,
aerosol concenations and solar-radiation levels as well as meteorological data. molina: we have to measure the pressure, we measure the temperature we measure the relative humidity, and the wind speed -- the wind direction. these all affect the transport of the pollutants. narrator: the aerodyne team traveled to mexico city as part of the milagro campaign. to help monitor the plume, they set up their mobile lab in a unique, elevated location between t0 and t1, called pico de tres padres. we're about a thousand meters above each of these two sites. so we have an opportunity at this location to actually look at the lofted plume that's coming to us. narrator: in the morning this location has relatively clean air since it is above the boundary layer
a layer near the ground that does not mix well with the atmosphere above. this layer traps the pollution below in the basin of mexico city. but as the sun heats the earth the boundary layer rises. herndon: but what we're observing right now -- we're above the mixing height. all of the pollution and emissions that are taking place are not able to mix up and come up to this location. what happens is that the sun comes up and begins to heat the surface of the earth. and just like putting a pan of boiling water onto the stove, it begins to mix and boil, moving the air upward, upward. and so it mixes up and up and up. and we're located up here at this location and suddenly we begin to see much of the city pollution and emissions coming to us but it's a bit later than when the sun comes up. we're seng increases in carbon monoxide carbon dioxide, and nox.
narrator: as the sun peaks and continues through the afternoon, the pollutants chemically change as they react in the atmosphere. herndon: what we observed at t0 we saw a mixture of primary and secondary pollutant species. up here, the character of just about everything we have seen indicates that it's very secondary, very processed. so, from that point of view, we have an opportunity to look at the first steps as the plume is moving downwind as to what is happening, what changes are taking place in the composition of those emissions. narrator: in addition to ground sites, researchers also measured pollutants from airplanes and satellites to corroborate their data and to help track the plume. molina: it is very important for us to do an integrated measurement. in order for you to look at the outflow
not only do you need a ground base, but you also need to have a larger coverage, so the airplane is very essential. and then the satellite observation provide even larger into space. we wanted to use different techniques that complement each other so it's very important for us to have complementary measurements. it's important for us to have intercomparison. in fact, some of the measurements during the campaign were designed exactly for that purpose. narrator: long-term, milagro will lead to better models of how emissions are transported and transformed, helping countries manage and improve air quality. preliminary data show that the aerosol plume from mexico city travels outside the city and rises high into the troposphere. here, the prevailing high-altitude winds can potentially transport the pollutants long distances,
even across continents. but it will be many years before molina and her team have definitive results. molina: milagro -- right now we only finish the first phase one, the measurement, the observation stage. and then the next phase is now we are in the process of doing the data analysis so we have all of this tons and tons of data. then all this information are now fit into models. then we are going to present the results to the mexican government. narrator: while the mexican government has recently made strides in reducing emissions with stricter regulation policies and cleaner fuel, mexico city is just one of a growing number of megacities. molina: we hope that by studying mexico city use this as a case study then we can find out how would the future megacities that are coming up how would they influence the atmospheric compositions
on a larger regional-global scale. kolb: if we don't control the changes we make to the atmosphere, the atmosphere may begin to control how many of us are left on the planet. so it's vital that we understand what happens to the pollutants we emit, and we understand how to better control them so the planet can continue to be a habitable place for both people and the rest of the creatures we share it with.